This is a type of valve in which the force of compressed air against a diaphragm is opposed by the force of a spring to control the area of opening for a fluid stream. It consists of an actuator and a valve. The actuator moves the valves stem as the pressure on a spring loaded diaphragm changes.

Sizes range from 1/2″ upto 12″ in both screwed and flanged ends.

Types vary from Normally closed or Normally open and 2 way or 3 way.